How to Show Colorbar in Matplotlib

In this tutorial, we will discuss how to show a colorbar in a matplotlib figure in Python.

To create a colorbar we have to use the matplotlib.pyplot.colorbar() function.

The following code shows a simple example of this.

import random
import matplotlib.pyplot as plt

s_x = random.sample(range(0, 100), 20)
s_y = random.sample(range(0, 100), 20)

s = plt.scatter(s_x, s_y, c=s_x, cmap="viridis")

c = plt.colorbar()

In the above example, we created a simple colorbar placed outside of the plot. We specified the colormap using the cmap parameter.

We can also specify the axes in which we wish to show the colorbar. If we wish, we can add it over the axes of the plot.

For example,

import random
import matplotlib.pyplot as plt

s_x = random.sample(range(0, 100), 20)
s_y = random.sample(range(0, 100), 20)

fig, ax = plt.subplots()
cax = fig.add_axes([0.27, 0.8, 0.5, 0.05])

im = ax.scatter(s_x, s_y, c=s_x, cmap="viridis")
fig.colorbar(im, cax=cax, orientation="horizontal")

In the above example, we used the subplots() function to get the figure and axes objects and use it to create the axes for the colorbar. We specified this using the cax parameter in the colorbar() function.

Also, note the use of the orientation parameter which altered the orientation of the final color bar. Apart from this, we can use different parameters to control the shape and size of the colorbar. For example, shrink can reduce the size of the colorbar by a small margin, aspect, which is the ratio of the sides of the bar, and there are many more.